The present invention relates to an electric heating device suitable for the heating of fluid food materials, for example, liquid food materials with high viscosity such as mayonnaise, fruit sauce, miso (fermented soybean paste) or the like; mixtures obtained by mixing water with tea powder, coffee powder, herb powder, powder of chicken bones used to make soup stock, or the like; and solid-liquid mixed food materials in which a solid and a liquid are mixed, such as a jam with fruit pieces or the like.
It is well known that food materials are in many cases heated for the purpose of sterilization and processing during the production of the food materials. Recently, in the production of various kinds of drinks or soups or the like, powders of tea, coffee, chicken bones or the like and liquid such as water or the like are mixed and the mixture has been heated in order to extract essential ingredients from the powders of tea or the like.
As a method of heating a food material, in recent years, an electric heating method of carrying electricity through the food material to generate heat by the use of electric resistance of the food material itself, namely, a Joule heating method has been paid attention to. So, using such an electric heating method has been tried also concerning the fluid food material such as a liquid food material and a solid-liquid mixed food material and the like.
As a conventional device for use in the electric heating of the fluid food material, there is a device having a cubic or rectangular container in which a pair of electrodes is provided so as to be opposite to each other on the inner surfaces thereof. So, electricity is carried through the food material between the pair of electrodes in the container, and the electric heating device becomes a batch type. If a food material with high viscosity is heated in such a device, since natural convection hardly occurs in the container, it is impossible to uniformly heat the food material because natural convection is difficult to create in the container. For its solution, it is also thought to provide rotatable stirring blades in the container to stir the food material during the electric heating. In this case, however, the four corner portions of the square container become dead spaces, and the food material at and around the portions is not sufficiently stirred. Accordingly, it is difficult to uniformly heat the food material.
If the container is formed in a cylindrical shape, the dead spaces at the stirring can be eliminated. In this case, however, the pair of electrodes opposite to each other are formed in a curved shape along the inner circumferential surface of the container, and so the distance between the central portions of the pair of electrodes differs from that between the edge portions of the pair of electrodes. As a result, the current density distribution at the time of the electric heating also becomes non-uniform, and thus it is impossible to uniformly heat the food material.
In addition, as a device for the continuous electric heating of the fluid food material, as disclosed in Japanese Patent Publication No. 2793473, the device is of such a type that ring-shaped electrodes are provided in a pipe line at predetermined intervals. Also, a device is put into practical use, in which electricity is carried between the upper ring-shaped electrode and the lower ring-shaped electrode during the continuously flow of the fluid food material into the pipe line and in which the food material is continuously heated by carrying electricity. However, it is apt to be difficult to continuously flow the food material with high viscosity and the solid-liquid mixed food material into the pipe line. Generally, for continuously flowing the fluid food material into the pipe line, the fluid food material contained in a hopper is compressed and transported by a pump. However, the pump must output high power in the case of using the food material with high viscosity, and the bridge phenomenon of a solid occurs in a hopper in the case of the solid-liquid mixed food material, which makes it impossible to carry the solid therein.
In the case where a continuously electric heating device is used for the extraction of the essential ingredients of tea or the like, the powder of tea leaf and water are mixed and the mixture is continuously compressed and transported. However, since the electric heating for a long time of 20 to 30 minutes or more than 30 minutes is required for such extraction and the length of the pipe line must be increased for performing the long-time electric heating, the size of the heating device is inevitably increased.
Therefore, with respect to the food material with high viscosity and the solid-liquid mixed food material, it is indispensable to apply the batch-type electric heating device. However, as described above, in the batch-type electric heating device, there have arisen problems of the aspects of the uniform heating, the spark occurrence, the burnt deposit of the food material, and the like.
An object of the present invention is to provide a batch-type electric heating device for heating a liquid food material with high viscosity and a solid-liquid mixed food material in which a solid and a liquid are mixed.
Another object of the present invention is to provide an electric heating device capable of uniformly heating the food material in the container without producing sparks and burnt deposit of the food material.
Another object of the present invention is to provide an electric heating device capable of heating the food material for a long time, like the case of the production of an extract.
An electric heating device of the present invention is a device for heating a fluid food material by Joule heat generated by carrying a current through the fluid food material, and comprises: a cylindrical container body for containing the fluid food material, an opening being provided at the upper end of the container body and a bottom wall being provided at the lower end thereof; a cylindrical outer electrode incorporated in said container body; an inner electrode arranged at the center portion of said container body and having an outer circumferential surface which is a cylindrical surface facing to said outer electrode; a power supply for supplying power to said inner electrode and said outer electrode; and a driving means for relatively rotating said inner electrode relative to said outer electrode, wherein the fluid food material is heated by carrying the current from said inner electrode and said outer electrode while said inner electrode is relatively rotated relative to said outer electrode. In the present invention, the fluid food material with high viscosity and the solid-liquid mixed food material in which a solid and a liquid are mixed are contacted smoothly and in the rotational direction thereof to the inner electrode and the outer electrode by relatively rotating the inner electrode and the outer electrode. Therefore, it is possible to prevent the adhesion of the burnt deposit of the food material to the electrode surface and the occurrence of the scales. In addition, it is also possible to perform the long-time heating of the food material so that the ingredients in the solid substance are extracted into the liquid.
In the electric heating device of the present invention, said container body is fixed and said inner electrode is rotated.
In the electric heating device of the present invention, said inner electrode is fixed and said container body is rotated.
In the electric heating device of the present invention, both of said inner electrode and said container body are rotatably driven, and the rotational directions of said inner electrode and said container body are reverse to each other.
In the electric heating device of the present invention, the device further comprises an electrode plate functioning as an intermediate electrode, the electrode plate being opposed to said outer electrode and extending in an axial direction and being attached to and electrically connected to said inner electrode. By providing the intermediate electrode to the inner electrode, it is possible to increase the surface area of the electrode including the inner electrode and facing to the outer electrode. Therefore, the conduction efficiency can be enhanced.
In the electric heating device of the present invention, the device further comprises a scraper attached to said inner electrode and slidably contacting to the inner circumferential surface of said outer electrode. By providing the scraper to the inner electrode, it is possible to prevent the adhesion of the food material to the inner circumferential surface of the outer electrode.
In the electric heating device of the present invention, the device further comprises a stirring member attached to said inner electrode and stirring the food material contained in said container body. By providing the stirring member to the inner electrode, the food material in the container body is sufficiently stirred, and thus it is possible to heat the food material at uniform temperature as a whole.
In the electric heating device of the present invention, said container body includes an outer container and a conductive container incorporated in the outer container to form said outer electrode, and a medium path through which a heating medium for preliminarily heating said outer electrode or a cooling medium for cooling said outer electrode flows is formed between said outer container and said outer electrode. By forming the medium path in the container body, it is possible to perform the preliminary heating of the container body and to prevent the overheating of the container body.
In the electric heating device of the present invention, a cooling medium path is formed in said inner electrode. By forming the cooling medium path in the inner electrode, it is possible to prevent the overheating of the inner electrode.